Find Original Cost Per Pound

Three pounds of coffee and 6 pounds of butter cost $5.20. A month later, the price of the coffee advanced 10% and that of butter 20%, making the total $5.86. Find the original cost of a pound of each.

original cost of a pound of coffee = x
original cost of a pound of butter = y

3x+6y=5.20
x+2y=26/15 =>x=26/15-2y

10% extra means 1.1 and 20% extra means 1.2

3(1.1x)+6(1.2y)=5.86

3.3x+7.2y=5.86

3.3(26/15-2y)+7.2y=5.86

143/25-6.6y+7.2y=5.86

0.6y=7/50

y=7/30

x=26/15 -2(7/30) =>x=19/15

cost of a pound of coffee is 7/30≈0.2333 and the cost of a pound of butter is 19/15≈1.2666

5.86 = 1.2 * X + 1.1 * Y
Solve for X & Y given that X + Y = 5.20

Can U dig it?